Bruce' FPV Diversity Controller project

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Bruce' FPV Diversity Controller project

Postby AltechMYOB » Sun Mar 25, 2012 3:36 pm

Hi Bruce... I know you strive to keep the costs of these projects at rock bottom so all can play, however did you consider incorporating any better checking on the video signal other than checking RSSI level?

eg. "Mr. RC-Cam" 'floated' an idea to make use of a Maxim loss-of-sync alarm IC (SOT23) "in under 5mS". Single unit price around $3 I believe.
Data sheet - URL http://datasheets.maxim-ic.com/en/ds/MAX7461.pdf

Perhaps there's an even better / cheaper part?

Just spit balling... :) design is way out of my league!

Edit: Oh... just watched the vid. To late, no room. Perhaps for a later version?
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Re: Bruce' FPV Diversity Controller project

Postby RCModelReviews » Mon Mar 26, 2012 6:48 am

RSSI is the easiest (and is generally pretty reliable if you're using circular polarization) method of switching.

Another method is to listen for noise on the audio channel -- just like the squelch on a 2-way radio does. If there is noise on the audio then that means the signal is low. That's because the audio channel is FM which automatically quietens when the signal is above a certain threshold.

I'll do some testing with the simple low-cost diversity switch and see how it goes -- there's still room for some changes ;-)
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Re: Bruce' FPV Diversity Controller project

Postby AltechMYOB » Mon Mar 26, 2012 2:24 pm

RCModelReviews wrote:RSSI is the easiest (and is generally pretty reliable if you're using circular polarization) method of switching.


hmmm... good tip. Looks like IBCrazy to NOT use CP for ALL vid links now.



RCModelReviews wrote:Another method is to listen for noise on the audio channel -- just like the squelch on a 2-way radio does. If there is noise on the audio then that means the signal is low. That's because the audio channel is FM which automatically quietens when the signal is above a certain threshold.


hmmm... I'm reminded of a former life when I maintained a full broadcast-spec TV station with satellite distribution. To earn an extra few bucks of a night time I filled the role of Master Control. Monitoring the down link from the satellite, whenever the link started to fade due to torrential rain downpour, it was always the audio that started to fade first. Only the very worst of weather took out the vision as well. Since I moved to a place where I need to do some improvements to the TV antenna reception, I note this same phenomenon with regard to digital TV reception as well. Seems to be a rule of the electromagnetic universe, where AV are concerned, that is.

RCModelReviews wrote:I'll do some testing with the simple low-cost diversity switch and see how it goes -- there's still room for some changes ;-)


viva-evolution :) but ONLY when needed!


cheers B
Last edited by AltechMYOB on Wed Apr 04, 2012 4:33 pm, edited 1 time in total.
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Re: Bruce' FPV Diversity Controller project

Postby baggus » Sun Apr 01, 2012 10:47 pm

@Bruce: How are you planning to handle differences in RSSI voltages (for example between different brand receivers) in your diversity system?
What if my lawmate receiver puts out a higher voltage than the BEVRC one although the signal on the latter is better? Shouldn't there be some small pots on the diversity controller to finetune this?
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Re: Bruce' FPV Diversity Controller project

Postby RCModelReviews » Mon Apr 02, 2012 1:13 am

All done in firmware -- a simple calibration routine sets the max/min signal voltages for each input.
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Re: Bruce' FPV Diversity Controller project

Postby Barnie » Tue May 01, 2012 9:48 pm

Hi Bruce,

I saw your recent video with the helical antenna and the cloverleaf together.

Now I thought; if you put three helical to the horizont and fly from the beginning e.g. to the south, if from the north you get a signal from e.g. a surveilance cam or another fpv which is a very low signal. Once you will be far away to the south your diversity could switch upon a time to this other signal when it becomes better than your plane's. This could lead in a "hijacked" signal and you will loose your plane.

What about a button like auto/manual1/manual2/manual/3... where you can toggle through the input channels, just in case to force the right signal??

regards
Bernd
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Re: Bruce' FPV Diversity Controller project

Postby T3PRanch » Wed May 02, 2012 5:18 pm

I can't wait to get a look at the schematic for this board. I plan to make a board that can accept the receiver modules as a plug in mounted on pin headers. Should make for a very compact 4ch diversity receiver.

Here is the receiver module I plan to use. http://www.hktdc.com/suppliers-products ... B/1525522/


Thurmond
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Re: Bruce' FPV Diversity Controller project

Postby AltechMYOB » Wed May 02, 2012 5:57 pm

Barnie wrote:Hi Bruce,

I saw your recent video with the helical antenna and the cloverleaf together.

Now I thought; if you put three helical to the horizont and fly from the beginning e.g. to the south, if from the north you get a signal from e.g. a surveilance cam or another fpv which is a very low signal. Once you will be far away to the south your diversity could switch upon a time to this other signal when it becomes better than your plane's. This could lead in a "hijacked" signal and you will loose your plane.

What about a button like auto/manual1/manual2/manual/3... where you can toggle through the input channels, just in case to force the right signal??

regards
Bernd


Hi...

I don't pretend to speak for Bruce... this is just my understanding -

I think Bruce is considering using 3 helical receiver antennas + their 3 associated video and audio receivers to cover a 180 degree arc for long range reception within that arc; plus the CP skewed co-plainer antenna for close-in work (eg. take off & landing) that will cover 360 degrees.

Additionally the video Tx and all of the Rx's are on 5.8Ghz... not much happening in that associated bandwidth really and especially where you would be flying your model.
IMHO if you are going to fly long range (and by that I mean the model is far enough away that you can't see it's attitude) ReturnToHome (A.K.A ReturnToLaunch) are pretty much mandatory requirements. There are also the Fail-safes built into the better RC controllers (eg. FrSky) to help. If on the off chance you do encounter some interference in your received AV signal (the facility providing your FPV view-point) regardless of it's origin then a simple switch on your RC will bring your model back to you and at some point on it's way back you will probably have your FPV signal available again.

Anybody else see it differently?
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Re: Bruce' FPV Diversity Controller project

Postby AltechMYOB » Wed May 02, 2012 6:16 pm

T3PRanch wrote:I can't wait to get a look at the schematic for this board. I plan to make a board that can accept the receiver modules as a plug in mounted on pin headers. Should make for a very compact 4ch diversity receiver.

Here is the receiver module I plan to use. http://www.hktdc.com/suppliers-products ... B/1525522/


Thurmond


hmm... did you note the minimum order number of 10?
Have you made sure that the rx channels are the right frequency for Bruce' recommended tx, or do you intend to buy a different one that will match your intended receivers?

Amazing what $9.40US can buy these days!

I'll wait to see Bruce' Rx design before considering anything else... especially regarding receiver sensitivity! :mrgreen:

Good luck with your design.
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Re: Bruce' FPV Diversity Controller project

Postby T3PRanch » Wed May 02, 2012 7:06 pm

AltechMYOB wrote:
T3PRanch wrote:I can't wait to get a look at the schematic for this board. I plan to make a board that can accept the receiver modules as a plug in mounted on pin headers. Should make for a very compact 4ch diversity receiver.

Here is the receiver module I plan to use. http://www.hktdc.com/suppliers-products ... B/1525522/


Thurmond


hmm... did you note the minimum order number of 10?

YES I did note the minimum order but friends can use them too. The same module is available in single quantities from multiple vendors as well but the price is about double.

Have you made sure that the rx channels are the right frequency for Bruce' recommended tx, or do you intend to buy a different one that will match your intended receivers?

They are the same. Most all modules I have found are all the same except for fat shark. They are different frequencies.

Amazing what $9.40US can buy these days!

I'll wait to see Bruce' Rx design before considering anything else... especially regarding receiver sensitivity! :mrgreen:

I am certainly not ordering in parts till I see the design as well

Good luck with your design.
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